Having once passed this narrow space the finger will be in the Spigelian recess and can palpate its boundaries. Further progress cephalad and to the right is barred by the diaphragmatic adhesions of the liver just detailed. But in the direction downward behind the lesser omentum and along the dorsal surface of the stomach, as well as to the left toward the spleen the excursion is limited only by the length of the examining finger. After opening the abdominal cavity of the human adult, elevating the liver and depressing the stomach, the hepatic attachment of the lesser omentum can be traced as already described. It will then be observed that the gastric attachment of the membrane lies in one plane following the lesser curvature while the hepatic attachment forms a broken line, with the angle situated at the left extremity of the transverse fissure. The vertical segment of the hepatic attachment, occupying the fissure for the ductus venosus, turns at this angle into the transverse segment which follows the transverse fissure to its right extremity where the two layers pass into each other around the right free omental margin (hepato-duodenal ligament). Consequently we overlook, in an abdominal cavity thus exposed, the entire caudal surface of the liver, including the caudal surfaces of right, left, and quadrate lobes. The junction of right and caudate lobes can be seen between vena cava and right edge of the omentum, or rather, it can be felt at this point. But the Spigelian lobe, turning its surface dorsad against the parietal peritoneum covering the diaphragm, forms part of the "posterior" liver surface and is not visible, although--as just stated, it can be palpated by passing the finger through the foramen of Winslow. The Spigelian lobe cannot be overlooked in its entire extent until the liver is removed from the body and regarded from behind. The caudal edge (continuation of its right angle into the caudate lobe and papillary tubercle) can be seen by tearing through the layers of the lesser omentum and lifting the liver up forcibly (Fig. 286). =Caudal Boundary of Foramen of Winslow.=--We have above referred to the fact that the finger introduced through the foramen of Winslow meets in this canal with resistance if an attempt is made to pass downwards. After passing this constricting point the free excursion into the Spigelian recess and behind the omentum and stomach and toward the spleen can be performed. In considering the elements which produce this narrowing of the communication between the two peritoneal sacs at the foramen of Winslow we have to deal with two factors, one primary and constant, the other secondary and inconstant. 1. The first of these is afforded by the arrangement of the arterial vessel supplying the liver. The hepatic artery is a branch of the coeliac axis, furnishing arterial blood to the liver tissues and supplying, in addition, branches to the stomach, duodenum and pancreas.